This disclosure is based on a connector plug for connecting an ignition coil to a spark plug. Connector plugs of this type are generally known from DE 10 2011 082 231 A1, JP 2011-134857 A and DE 10 2015 110 309 A1, for example.
Depending on the geometric conditions on an engine, connector plugs with either a straight or a curved protective tube are required. The production of both straight and curved protective tubes is expensive. There is therefore a need for connector plugs that can be bent as required, such as the connector plug of known art from JP 2011-134857 A.
This disclosure shows how a connector plug for connecting a spark plug to an ignition coil can be produced cost-effectively, which—if required—can also be mounted in a curved state on an engine with little effort, and is protected from damage by a mechanically robust protective tube.
The protective tube of an inventive connector plug has a predetermined bending point with a reduced bending stiffness. If the connector plug is to be used in a curved state, the protective tube can easily be bent in the desired manner at the one or more bending points, so that the connector plug can be used in either a straight configuration or a curved configuration. In the simplest case, the predetermined bending point can be embodied as a groove or a notch in the outer surface of the protective tube.
In an advantageous refinement of this disclosure the protective tube has a plurality of mutually adjacent reinforcement ribs extending in its longitudinal direction, wherein the predetermined bending point is designed as a recess, or other weakening feature, in one or a plurality of these reinforcement ribs. All the reinforcement ribs, some of the reinforcement ribs, or even just one reinforcement rib, may have such a recess.
It is preferable that reinforcement ribs on opposite sides of the protective tube have a predetermined bending point in the form of a recess, but that reinforcement ribs located in between them have no recess. In this manner, the bending stiffness of the protective tube is reduced only where it is necessary, namely on the inner and outer radius of the intended bend.
The protective tube can have, for example, four reinforcement ribs, wherein two opposing reinforcement ribs have the predetermined bending point, and the two reinforcement ribs located in between them have no predetermined bending point at the corresponding position. The recess forming a predetermined bending point can, for example, be designed in the form of a notch, a rectangular shape, or a U-shaped recess.
In another advantageous refinement of this disclosure the outer surface of the protective tube is closed in the vicinity of the predetermined bending point. In this manner, the protective function of the protective tube is not impaired by the predetermined bending point. In particular, the protective tube can then also fulfil the function of electrical insulation such that no additional electrical insulation is required. In principle, the protective tube can, however, also fulfil its function, albeit to a limited extent, if the predetermined bending point forms an opening in the outer surface of the protective tube, for example a slot passing through its wall.
In another advantageous refinement the protective tube has, at a distance from the predetermined bending point, a section that has an increased wall thickness. In the vicinity of the predetermined bending point, on the other hand, the wall thickness of the protective tube between the reinforcement ribs can be reduced.
The protective tube of an inventive connector plug can have a plurality of predetermined bending points, which are arranged at a distance from each other in the axial direction. However, the protective tube preferably only has one predetermined bending point at one height.